1. Field of The Invention
This invention relates to a photosensitive resin composition which has wide utility in the fields of protective insulating films for semiconductor devices, alignment films for liquid crystal display devices and insulating films for multi-layered printed boards. The invention also relates to heat-resistant cured products obtained from the composition, particularly heat-resistant cured films for protecting heat-resistant electronic parts.
2. Description of the Prior Art
A number of heat-resistant photosensitive materials have been heretofore proposed including, for example, materials comprising polyamic acids and bichromates (U.S. Pat. No. 3,623,870), materials which comprise polyamic acids whose carboxyl groups are introduced with photosensitive groups through ester bonds (U.S. Pat. No. 3,957,512 and Japanese Laid-open Patent Application No. 55-45746), and materials comprising polyamic acids whose carboxyl groups are introduced with photosensitive groups through amido bonds (U.S. Pat. Nos. 4,515,887 and 4,587,204). Further, there have been proposed materials which comprise polyamic acids whose carboxyl groups are introduced with photosensitive groups through silyl ester bonds (Japanese Laid-open Patent Application No. 62-275129) and materials which comprise polyamic acids and amine compounds having photosensitive groups (U.S. Pat. No. 4,243,743).
However, these materials still have problems in the incorporation of ionic impurities for the materials of U.S. Pat. Nos. 3,623,870 and 3,957,512, in swelling at the time of development for the materials of U.S. Pat. Nos. 3,957,512, 4,515,887 and 4,587,204 and Japanese Laid-open patent application No. 55-45746, and in the sensitive stability for the materials of Japanese Laid-open Patent Application Nos. 62-275129 and U.S. Pat. No. 4,243,743.
In order to solve the above problems, there has been proposed a positive photosensitive resin composition which comprises polyimide resins having a phenolic group and naphthoquinone diazidosulfonate (Polymer Engineering And Science, July 1989, Vol. 29, 954). However, this photosensitive resin composition has to make use of a specific type of polyimide, coupled with another problem that the phenolic groups are liable to remain after formation of the film. The phenolic groups left in the film will cause the resin to have an increasing water absorption. This is not favorable when such a composition is applied to electronic parts. Alternatively, U.S. Pat. No. 5,104,768 sets out a photosensitive resin composition which comprises esterified polyamic acids and photosensitive quinonediazides. This composition essentially requires an alkaline aqueous solution of a high concentration for development. In addition, it undesirably takes a long time for the development. Thus, the composition is not suitable for practical applications.